build: Revert back to only phpunit 9.x

Author: DannyvdSluijs

composer.json

@@ -25,7 +25,7 @@
         "enlightn/security-checker": "^1.10 || ^2.0",
         "guzzlehttp/guzzle": "^6.5.8 || ^7.4.5",
         "guzzlehttp/psr7": "^1.9.1 || ^2.4.5",
-        "phpunit/phpunit": "^9.0 || ^10.5",
+        "phpunit/phpunit": "^9.0",
         "symfony/mailer": "^6.0 || ^7.0"
     },
     "config": {